[PATCH v2 11/21] arm: socfpga: Secure register access for clock manager (SoC 64bits)

[Ang, Chee Hong]

From: Ang, Chee Hong
Sent: Saturday, February 22, 2020 6:00 PM
To: Simon Goldschmidt <simon.k.r.goldschmidt at gmail.com>
Cc: U-Boot Mailing List <u-boot at lists.denx.de>; Marek Vasut <marex at denx.de>; See, Chin Liang <chin.liang.see at intel.com>; Tan, Ley Foon <ley.foon.tan at intel.com>; Westergreen, Dalon <dalon.westergreen at intel.com>; Gong, Richard <richard.gong at intel.com>
Subject: RE: [PATCH v2 11/21] arm: socfpga: Secure register access for clock manager (SoC 64bits)

Ang, Chee Hong <chee.hong.ang at intel.com<mailto:chee.hong.ang at intel.com>> schrieb am Sa., 22. Feb. 2020, 06:30:
> From: Chee Hong Ang <chee.hong.ang at intel.com<mailto:chee.hong.ang at intel.com>>
>
> Allow clock manager driver to access the System Manager's Boot Scratch
> Register 0 in non-secure mode (EL2) on SoC 64bits platform.
>
> Signed-off-by: Chee Hong Ang <chee.hong.ang at intel.com<mailto:chee.hong.ang at intel.com>>
> ---
>  arch/arm/mach-socfpga/clock_manager_agilex.c | 5 +++--
>  arch/arm/mach-socfpga/clock_manager_s10.c    | 5 +++--
>  2 files changed, 6 insertions(+), 4 deletions(-)
>
> diff --git a/arch/arm/mach-socfpga/clock_manager_agilex.c b/arch/arm/mach-
> socfpga/clock_manager_agilex.c
> index 4ee2b7b..e5a0998 100644
> --- a/arch/arm/mach-socfpga/clock_manager_agilex.c
> +++ b/arch/arm/mach-socfpga/clock_manager_agilex.c
> @@ -12,6 +12,7 @@
>  #include <asm/arch/system_manager.h>
>  #include <asm/io.h>
>  #include <dt-bindings/clock/agilex-clock.h>
> +#include <asm/arch/secure_reg_helper.h>
>
>  DECLARE_GLOBAL_DATA_PTR;
>
> @@ -65,8 +66,8 @@ unsigned int cm_get_l4_sys_free_clk_hz(void)
>
>  u32 cm_get_qspi_controller_clk_hz(void)
>  {
> -     return readl(socfpga_get_sysmgr_addr() +
> -                  SYSMGR_SOC64_BOOT_SCRATCH_COLD0);
> +     return socfpga_secure_reg_read32(socfpga_get_sysmgr_addr() +
> +
> SYSMGR_SOC64_BOOT_SCRATCH_COLD0);
>  }
>
>  void cm_print_clock_quick_summary(void)
> diff --git a/arch/arm/mach-socfpga/clock_manager_s10.c b/arch/arm/mach-
> socfpga/clock_manager_s10.c
> index 05e4212..02578cc 100644
> --- a/arch/arm/mach-socfpga/clock_manager_s10.c
> +++ b/arch/arm/mach-socfpga/clock_manager_s10.c
> @@ -9,6 +9,7 @@
>  #include <asm/arch/clock_manager.h>
>  #include <asm/arch/handoff_s10.h>
>  #include <asm/arch/system_manager.h>
> +#include <asm/arch/secure_reg_helper.h>
>
>  DECLARE_GLOBAL_DATA_PTR;
>
> @@ -385,8 +386,8 @@ unsigned int cm_get_l4_sp_clk_hz(void)
>
>  unsigned int cm_get_qspi_controller_clk_hz(void)
>  {
> -     return readl(socfpga_get_sysmgr_addr() +
> -                  SYSMGR_SOC64_BOOT_SCRATCH_COLD0);
> +     return socfpga_secure_reg_read32(socfpga_get_sysmgr_addr() +
> +
> SYSMGR_SOC64_BOOT_SCRATCH_COLD0);
>  }
>
>  unsigned int cm_get_spi_controller_clk_hz(void)
> --
> 2.7.4
>SPL reads the clock info from handoff table (OCRAM) and write
>the clock info into the System Manager's boot scratch register.
>U-Boot proper will read from the System Manager's boot scratch
>register to get the clock info in case the handoff table (OCRAM)
>is no longer available.
>After some investigations, the handoff table in OCRAM should be preserved
>for warm boot. In other words, this handoff table should be left untouched.
>SPL and U-Boot should directly read the clock info from handoff table in OCRAM.
>Therefore, U-Boot proper no longer need to read the clock info from
>System Manager's boot scratch register (secure zone) from non-secure world (EL2).

>I don't think that's a good idea: for security reasons, SPL memory should not be accessible from EL2 if it is required/used for the next reboot.
>
>Regards,
>Simon
Right. I think I will have to go for proper high-level API in ATF for EL2 to query the clock frequency:
INTEL_SIP_SMC_CLK_GET_QSPI

I found out System Manager is read only in EL2 and read/write in EL3.
Will drop this patch.
No change required since it only read back from System Manager’s registers.